The congressman office just responded to my inquiry that I made 2 days ago about my whole family's I-485:
“ The I 485 were approved 10/24/07 and the alien registration cards are in production for the parents. We do not have biometrics to make the child's card. We will be sending a biometrics appointment for the child.”
The conclusion is that a kid does need FP for card production. But they can give the approval notice first and then send the fingerprint notice for the kid.
Hope this is helpful.